BlackPointDetector.h

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/*
 * Copyright (c) Meta Platforms, Inc. and affiliates.
 *
 * This source code is licensed under the MIT license found in the
 * LICENSE file in the root directory of this source tree.
 */
 
#ifndef META_OCEAN_CV_ADVANCED_BLACK_POINT_DETECTOR_H
#define META_OCEAN_CV_ADVANCED_BLACK_POINT_DETECTOR_H
 
#include "ocean/cv/advanced/Advanced.h"
 
#include "ocean/base/Frame.h"
#include "ocean/base/Worker.h"
 
#include "ocean/cv/Histogram.h"
 
namespace Ocean
{
 
namespace CV
{
 
namespace Advanced
{
 
/**
 * Provides functions for black point detection in a frame.
 * @ingroup cvadvanced
 */
class OCEAN_CV_ADVANCED_EXPORT BlackPointDetector
{
    public:
 
        /**
         * Definition of a vector holding 32 bit floating point values.
         */
        typedef std::vector<float> Color;
 
    public:
 
        /**
         * Attempts to detect the black point in the given frame with three channels.
         * @param frame The frame in which the black-point will be detected, must be valid
         * @param worker Optional worker object to distribute the computation
         * @return The resulting color of the black points, one for each channel
         * @return True, if the detection was successful
         */
        static Color detectBlackPointHistogram(const Frame& frame, Worker* worker = nullptr);
 
        /**
         * Attempts to detect the black point in the given frame with three channels.
         * @param frame The frame in which the black-point will be detected, must be valid
         * @param width The width of the frame in pixel, with range [1, infinity)
         * @param height The height of the frame in pixel, with range [1, infinity)
         * @param framePaddingElements The number of padding elements at the end of each frame row, in elements, with range [0, infinity)
         * @param worker Optional worker object to distribute the computation
         * @return The resulting color of the black points, one for each channel
         * @return True, if the detection was successful
         */
        template <unsigned int tChannels>
        static Color detectBlackPointHistogram8BitPerChannel(const uint8_t* frame, const unsigned int width, const unsigned int height, const unsigned int framePaddingElements, Worker* worker = nullptr);
};
 
template <unsigned int tChannels>
BlackPointDetector::Color BlackPointDetector::detectBlackPointHistogram8BitPerChannel(const uint8_t* frame, const unsigned int width, const unsigned int height, const unsigned int framePaddingElements, Worker* worker)
{
    static_assert(tChannels != 0u, "Invalid channel number!");
    ocean_assert(frame && width != 0u && height != 0u);
 
    Color blackPointColor(tChannels);
 
    const CV::Histogram::Histogram8BitPerChannel<tChannels> histogram(CV::Histogram::determineHistogram8BitPerChannel<tChannels>(frame, width, height, framePaddingElements, worker));
 
    const unsigned int threshold = max(1u, (width * height + 1000u) / 2000u); // 0.05 % of number of pixels
 
    constexpr float inv255 = 1.0f / 255.0f;
 
    for (unsigned int c = 0u; c < tChannels; c++)
    {
        const unsigned int* bins = histogram.bins(c);
 
        // we iterates through the histogram from (channel-wise) lowest to highest bin to find the first bin that has more votes than the specified threshold
 
        for (unsigned int i = 0u; i < 256u; ++i)
        {
            if (bins[i] >= threshold)
            {
                blackPointColor[c] = float(i) * inv255;
                break;
            }
        }
    }
 
    return blackPointColor;
}
 
}
 
}
 
}
 
#endif // META_OCEAN_CV_ADVANCED_BLACK_POINT_DETECTOR_H